HH bassmachine 250watt bass head. Missing mosfets

[blindboybenton]

Hi All

Ive just been given the above. Its needs output mosfets and they are all missing. Does anyone know what they are or what can be fitted. Also if you have a schematic that might help me aswell.Im going to sell this on when repaired so i want to keep the cost down by not buying the schematic from MAJ electronics



BBB

[J M Fahey]

It probably has expensive Lateral Mosfets, each one costing as much or more than the schematic.
Meaning just 1 (one) needlessly burnt is more than what you are "saving".

As a reference, study this MosFet HH900W power amp, meaning it has 2 450W channels.
HH-ELECTRONIC M900 Service Manual free download, schematics, eeprom, repair info for electronics

Yours is probably *very* similar to one channel, with somewhat less +/-V rails, and maybe just 4 (or 6) power transistors instead of 8.

There's a reason the one they gave you is missing its MosFets, a reason called $$$$$$

Hand draw a rough schematic of the power section, at least biasing and end side, comparing it with the 900W schematic, I bet they are closer than cousins.

[Enzo]

If MAJ asks only L5 (I have no idea how to make the pound symbol here) for a schematic emailed back, I have to wonder how much time is it worth looking for a free one?

[blindboybenton]

Hi

The guy who gave me the amp said that they need changing. He is a retired engineer and had removed them years ago and then stuck the amp in the roof for years. Ill speak to MAJ about it later on in the week. Was hoping somebody on here will have schematic.

BBB

[Jazz P Bass]

Have you attempted to contact MAJ?

MAJ Electronic

[blindboybenton]

hello blindboy
I have one of these amps myself . Just checked it the orginal fet is HH HFN 7945 and some of mine have been replaced before i brought it with 2SK135
RS components at £7.07 ea + Vat and PP brings it out at about £50 +

Hope this helps

Bassman

[blindboybenton]

Thanks mate

If i get the schematic and the fets there is very little profit as i will get upto a £100 max

BBB

[MarkusBass]

Slightly cheaper replacements: ECF10N20 . Also P-channel transistors are available from this company.
How many transistors do you need?

Mark

[J M Fahey]

Buying/getting dead stuff and repairing it for sale on EBay is not usually profitable.
Now the point is, supposing you actually need it: can you get a properly working MosFet , British made 250W RMS bass head for 100 Pounds?

[blindboybenton]

Buying/getting dead stuff and repairing it for sale on EBay is not usually profitable.
Now the point is, supposing you actually need it: can you get a properly working MosFet , British made 250W RMS bass head for 100 Pounds?

I didnt buy it i was given it. If i try and sell maybe £100. i will give it a go

[blindboybenton]

6 in total, may give them a call. something too do when i quite, not this week for sure